A method of producing peptides by utilizing Bombyx mori nuclear polyhedrosis virus (BmNPV) has already been reported (Reference 1; for the references cited herein, see the end hereof).
The central feature of this method consists in constructing a recombinant BmNPV with a structural gene for a desired protein replacing the polyhedral protein-encoding structural gene portion using recombinant DNA techniques and propagating the recombinant in cultured silkworm (Bombyx mori ) cells or in living silkworms (Bombyx mori ) to thereby accumulate the desired protein therein. However, this method is still unsatisfactory with respect to the yields of the desired proteins.
Moreover, the production of fused proteins is already in practice in Escherichia coli. The yields cannot be said to have been improved significantly, however (References 2-8).